GFS2: Fix mount hang caused by certain access pattern to sysfs files

commit 19237039 upstream.

Depending upon the order of userspace/kernel during the
mount process, this can result in a hang without the
_all version of the completion.

Signed-off-by: Steven Whitehouse <swhiteho@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>